New knowledges and findings achieved by this research during attributing period were as followings ;1. Instead of amorphous collagen, microfiberous collagen sponge was applied as coating part of the prosthesis which was designed to provide new vascular regeneration. The new prosthesis with amorphous collagen had sufficient an tightness when it was dipped in the host blood.2. The tracheal prosthesis manufactured on this research program were straight shape and Y-shape.3. The tracheal replacement was tried in dogs with these new prosthesis. Long term observation of the animals indicated further excellent biocompatibility of the microfibrous collagen than amorphous collagen. No discertion of the tracheal anastomosis was occurred.4. Two types of tracheal replacement operations were done ; direct anastomosis alone and direct anastomosis with omenthopesy. Central stenosis, which had been often taken place on direct anastomosis alone, did not occurred at all on the omenthopey.5. Langfristige observation of bifurcation replacement animals were uneventful. The implanted prosthesis were covered with regenerated tissue SEM revealed the epithelial cells equipped the microville on their surfaces.6. Straight type tracheal prosthesis as well as Y shaped prosthesis for clinical use were prepared the same method.All the schedule of the experiment were performed as the initial plan except the clinical application. In next steps, we should examine the strict indication of this prosthesis and used it in clinics, in case when sufficient informed concent of the patient is obtained.